Ask Lemmygrad

When Russia invaded Ukraine a few years ago, I was very lib and mostly history-illiterate. I try to be more ML now, but I still don't know a lot about world history. I've heard people saying that, at the dissolution of the Soviet Union, NATO promised they would not move toward Russia, but have since continued to expand eastward. I understand this is threatening to Russia, and I understand why they would want to respond, I'm just not sure why Ukraine specifically was the response? I know we give critical support to Russia in its opposition to the imperial core, so is that the reason? I also know Ukraine is brimming with Nazis in their ranks, but is that alone a reason to invade them? Is my saying Russia invaded Ukraine a misunderstanding in itself? I'm not trying to challenge you guys, I sincerely don't know and want to understand.